Duplicating process



DUPLICATING PROCESS Robert J. Kliinkowski, Chicago, and Robert T. Florence, Park Ridge, Ill., assignors to A. B. Dick Company, Niles, Ill., a corporation of Illinois No Drawing. Original application July 7, 1952, Serial No. 297,568, new Patent No. 2,634,677, dated April 14, 1953. Divided and this application April 10, 1953, Serial No. 348,124

Claims; (Cl. 101-1494) This invention relates to a process for the reproduction of multiple copies and it relates more directly to the production of copies by a new and improved spirit duplicating system. This application is a division of our copending application Ser. No. 297,568, filed on July 7, 1952, now Patent No. 2,634,677, issued April 14, 1953.

To the present, reproduction processes of the type described have been effected by systems generally referred to in the art as the gelatin system and as the spirit duplieating system. In the gelatin system, a master sheet is imaged by typing, writing or drawing with an ink composition containing a water soluble dye, usually crystal violet. The image is transferred in reverse by absorption during contact into a gelatin compound disposed in a pan or on the surface of a transfer sheet which then forms the printing medium. The water soluble dyestufi transfers from the moist printing medium to form copy upon contact with impression medium.

In the spirit duplicating system, the image is formed in reverse on a master by transfer from a carbon type sheet coated with a composition containing a high proportion of a water soluble dye such as crystal violet, Victoria green, Victoria blue and the like. The image transfers from the master to copy sheets, the surfaces of which have been wetted with an alcohol or alcohol and water combination upon contact, as between a compression cylinder and a printing plate mounted in a rotary duplicating machine. The highly volatile solvents permit the production of a larger number of copies and provide for more rapid drying of the copy sheet to reduce setoflf and smear. In the spirit duplicating systems, the dyestuif is preferably contained in a coating such as in a carbon sheet for transfer in mirror image onto the printing master by the application of force or the like.

While hectograph systems of the type described are desirable because of their flexibility in use and simplicity in operation for the production of multiple copies in a rapid and economical manner, there are a number of serious objections which characterize the process as it is presently being practiced. Most of the objectionable characteristics stem from the highly dispersible fine particles characteristic of the dyestuffs and the highly soluble nature thereof in aqueous medium. The fine particle size of the dyestufi leads to objections in their use for the manufacture of the carbon transfer sheet or inking ribbon. In most manufacturing processes, the atmosphere within the formulating and coating room and the atmosphere for miles surrounding the building in which it is being used becomes contaminated with fine particles of the dyestufl whereby the personnel within the buildings and the territory surrounding the buildings acquire a purplish tint which is diflicult to remove.

Because of the highly Water soluble nature of the dyestulf, moisture on the hands of the operator is sufiicient to remove. substantial quantities of the dye onto the hands whereby it invariably spreads to other parts of the body and clothing. It is difficult to operate a hectograph sysice tern embodying such dyestuffs without staining ones hands and clothing.

The limitations with respect to the use of dyestuffs highly soluble in water and in spirit solvents has to the present limited color of copy reproduced to the dye colors formed of such compositions as crystal violet, rhodamine (red), Victoria blue or Victoria green. It is impossible to produce intense black copy or copy in any other color than the four defined or shades thereof. Attempts have been made to formulate a black by combining the various usable dyestuffs but the best that such combinations have been able to produce is gray copy and the ditferences in solubility of the various dyes causes differential leaching and gradual toning off of one color relative the other to produce copy of variable color quality from start to finish.

Important also is the inability to produce permanent copy because of the instability of the water soluble basic dyes especially upon exposure to light.

Finally it is difiicult to control the solvency of the dye or the effect of the medium in which it is contained with sufficient regularity to produce copy of uniform quality and often the number of copies of readable quality vary from time to time depending upon the conditions existing during reproduction.

It is an object of this invention to provide a hectograph system which is substantially free of the objectionable features of the prior art processes of the types described.

Another object is to provide a spirit duplicating system free of compounds capable of coloring or dirtying ones hands, clothing, the atmosphere or the environment during the manufacture and use of the elements employed.

A further object is to provide a spirit duplicating system in which permanent copy of good quality is produced.

Another object is to provide a spirit duplicating system in which the color of the copy can be varied over a fairly wide range and includes the production of intense black copy of good quality.

More specifically, it is an object of this invention to provide a new and improved spirit duplicating system and materials for use in same wherein the materials involved in the manufacture and use are incapable of transferring color and wherein the copy is developed in the copy sheet itself thereby to permit the production of copy with insoluble dyestuffs incapable of use in systems heretofore employed and which are sufliciently stable and insoluble to remain permanently in the copy sheet.

Briefly described, instead of forming the image on the master of a basic aniline dye highly soluble in water or spirit solvents, as in processes heretofore employed in gelatin or in spirit duplicating systems, the image herein, preferably in reverse,-is formed on the master of a water or alcohol soluble component of an azo dye and which has no objectionable color transfer value in the state in which it exists in the master or in the ink composition, inking ribbon or carbon sheet with which. the master is formed but which upon transfer to the copy sheet forms an azo dye by chemical reaction with other dye forming components contained in non-reactive state in the imaged master, or contained in the fluid with which the copy sheet is wetted for effecting transfer of the imaging component upon contact, or in the copy sheet or contained in a fluid applied to the copy sheet subsequent to transfer of the imaging material from the master.

The concepts of this invention are capable of a number of modifications which will hereinafter be described in greater detail and for purposes of illustration, but not of limitation, examples will now be given. of one mode for carrying out the inventive concepts embodied herein.

Example 1 p A carbon type transfer sheet is formed by coating a.

. 3 thin fibrous sheet with a composition compounded of the following materials:

The composition is reduced to molten state at a ternperature of about 8085 C. for application as a hot melt onto the surface of the base sheet in concentrations ranging from 20 pounds per 3000 square feet.

Example 2 For preparation of the imaged master, the coated sheet manufactured in accordance with Example 1 is positioned with the coated side in surface contact with the prepared surface of a suitable master sheet whereby material is displaced from the coating to the surface of the master to form the mirror image of forces applied against the uncoated side of the coated sheet as by a stylus, writing pen or pencil, typewriter key, die impression or the like.

To the present, the active ingredient in the coating composition for development of the image in the copy sheet comprises the paradiazo diethyl aniline zinc chloride which is a water and alcohol soluble component of an azo dye and which is free of any dye color thereby to provide for a clean process in the manufacture of the coated sheet and the imaged master. In the event that it is desirable to introduce some color for inspection of the imaged master, it is possible to compound the coating composition or the imaging composition with a minute amount of some coloring component selected of any one of the common pigments, dyestuffs or other coloring agents.

Example 3 For the production of multiple copies, the imaged master prepared in accordance with Example 2 is mounted on a cylinder of a rotary duplicating machine of the conventional type for hectograph duplication. The fluid applied to the surface of the copy sheet in advance of contact with the master may be formulated to contain the following:

Percent Phloroglucinol 0.5 b-Naphthol 5 .0 Diethanolamine 2.0

Methanol 92.5

As the wetted surface of the copy sheet moves into surface contact with the imaged master between the impression roller and the cylinder mounting the master, some of the diazo dye forming component is dissolved from the surface portion of the image whereupon coupling takes place between the phloroglucinol and the pdiazo diethyl aniline zinc chloride at pH levels adjusted by the dicthanolamine to form a relatively water insoluble and permanent deep purple dyestufr" in direct image in the copy sheet.

Color development rather quickly takes place once the dye component and coupler have been combined in the copy sheet in the presence of the alkaline medium to form the dyestuff. The copy sheet is capable of being handled almost immediately without fear of setoff or smear and the color produced is permanent in character.

The number of copies secured depends greatly upon the thickness of the coating of which the image is formed, the amount of dye forming component contained in the coating composition and the character and quantity of solvent applied to the copy sheet for effecting transfer of the dye component from the imaged master for coupling reaction to develop color. It will be apparent, however, that the intensity of the color capable of being developed by azo dye systems of the type described permits the production of readable copy with minimum concentration of dye forming component with the result that by proper control, up to to 500 copies may easily be secured from a single master.

It is believed that the amount of spirit solvent present on the copy sheet during contact with the master is suflicient to cause transfer of an infinitesimal proportion of the azo dye forming component present and that a minute portion of the carrier or wax base in which the dye component is contained is also removed to the copy sheet,

otherwise the dye forming component in the master sheet would be converted into a relatively Water insoluble dyestuff incapable of being transferred to form copy in accordance with the concepts of this invention.

Example 4 In the event that it is desired to produce red copy instead of purple from the master prepared in accordance with Example 2, the copy sheet is Wetted with a solution formulated of the following:

Phenylmethyl pyrazolone 5 .0 Diethanolamine 2.0 Methanol 93 .0

Upon contact between the imaged master and the surface of the copy sheet wetted with the above composition, some of the azo dye forming component transfers to the copy sheet to form a red azo dye upon coupling with the phenylmethyl pyrazolone in the presence of the base. As described before, drying occurs almost immediately so that although the intensity of the color continues to increase upon standing, the copy produced is incapable of setoff or smear.

Example 5 For the production of blue copy from the master prepared in accordance with Example 2, the copy sheet may be wetted in conventional manner with the following composition:

Percent 2,3-dihydroxy naphthalene, 6, sulfonic acid 5.0 Diethanolamine 8.0 Water 10.0 Methanol 77.0

Example 6 By way of a still further example, a suitable transfer sheet or a suitable imaging composition in aqueous dispersion or solvent solution for use in the practice of this invention may be compounded of the following composit1on:

Percent Carnauba wax 8.5 Oxidized microcrystalline wax 14.0 Dark petrolatum 12.0 Mineral oil (100 seconds viscosity) 15.5

Paradiazo-ethyl-hydroxy ethyl-aniline zinc chloride 50.0

on the surface of a suitable master sheet positioned insurface contact therewith.

Percent Dark purple copy may be produced from the master sheet imaged in accordance with Example 6 by use of a fluid corresponding to the composition of Example 3 for wetting out the surface of the copy sheet in advance of contact with the master. As many as 100 to 500 copies can be made before the dye forming diazo component is exhausted from the imaged master sheet. Red copy can be produced by use of the fluid of Example 4 for wetting out the surface of the copy sheet and the same master can be used to produce blue copy when the copy sheets are wetted with a fluid of Example 5.

The composition of the base in which the azo dye forming component is embodied in the manufacture of a coated carbon sheet is unimportant and other conventional compositions used in the manufacture of coated carbons may be used so long as the composition is capable of providing a coating on the base sheet which exists as a separate layer on the surface thereof withinsuflicient anchorage to-prevent transfer to the master surface to form the image thereon. Generally such compositions are formulated of waxy materials in various combinations including carnauba wax, microcrystalline wax, paraffin wax, ozokerite and the like, alone or in combination with softening agents such as mineral oils, fatty acids and the like. Modification to improve strength and film forming characteristics may include the addition of small amounts of polyethylene, polybutylene and other polymeric compounds formed of unsaturated aliphatics and other materials capable of compatibility with the waxy substances to form a stable composition. The composition of the base in which the dye component is contained should provide for a continuous layer capable of transfor to surfaces in contact therewith upon impression but it is preferred to formulate the composition of materials which have slight solubility in the spirit solvents so as continuously to cleanse the surface of the imaged master during production of copy.

While it is preferred to apply the carbon type coating composition as a hot melt in the manner described in Examples 1 and 6, it is possible to achieve the desired coating of the base sheet by application of the materials from solvent solutions or aqueous emulsions. However more than one coating will usually be required to achieve the desired coating weights on the base sheet. For example, the compositions of Examples 1 or 6 may be dissolved in ethyl acetate, trichloroethylene and the like alone or in combination with toluene or benzene diluents to form a 20-40 percent solution or the compositions of the type described may be dispersed in aqueous medium with a small amount of surface active agent to form a 40-60 percent aqueous emulsion. From the solvent solution of lower solids content more than one coating will be necessary to achieve the desired coating weight but generally one, or at most two coatings will be sutficient when coatings are prepared by the high solids content dispersions of the type described. Where high temperatures are not used to eliminate the diluents, almost any stable diazo dye forming component may be used, but where temperatures in excess of 80 C. are used for drying, the diazo component is limited because the great majority are unstable at such temperature levels. When the imaging material is contained in an inking ribbon or as a Writing composition with which the image may be formed directly onto the master, the limitations as to transferability are not paramount and compositions containing the diazo dye component in an oily or other fluid base may be used.

It is desirable to embody as high concentration of the dye component as possible in the imaging material, as in the carbon coating, consistent with the ability of the coating to maintain the desired film characteristics and strength. .Generally the amountof the dye forming component introduced as an ingredient in the coating composition depends on the ability to maintain suflicient fluidity under the condition of coating to achieve the desired application and coverage. For the production of a number of copies of sufficient intensity, it is advisable to maintain the concentration of dye component in excess of percent by weight and preferably in excess of 50 percent by weight. In general, fluidity of the de sired character falls off when the concentration reaches 75 percent by weight but more may be used, with the introduction of fluidizing agents.

For the diazo component, it is preferred to make use of a group of alcohol and water soluble diazo compounds which have been classified as active compounds stable in neutral or acid medium but which show the reaction of diazo ions upon solution in water. These may be classified as (1). the diazo compounds which are stable as the corresponding diazonium sulphates or chlorides, such as p-diazo diphenylamine sulphate, (2) diazo compounds which are stabilized as the corresponding Zinc chloride or other metallic chloride salt complexes, or (3) diazo compounds which are stabilized as salts of sulfonic acids or aryl sulfonic acids. The following structural formulae are representative of the general types of diazo compounds which may be used:

The corresponding stabilized zinc chloride complexes or sulfonates of groups 2 and 3 above may be represented by the following typical formulae:

(Ar-aryl) Couplers adapted to be used for combination with the diazo compounds in the practice of this invention should be capable of removal of a hydrogen ion for combination with the chloride ion of the diazo for dye formation. Such compounds are preferably selected of the organic aromatic compounds in the form of aromatic amines such as aniline or substituted aniline such as dimethylaniline, phenolic compounds such as phenol, resorcinol, phloroglucinol, 2,3-dihydroxy naphthalene 6- sulfonic acid and water soluble salts thereof; thio compounds such as thio-barbituric acid, or cyano compounds such as cyanoacetarnine; pyrazolone or derivatives.

Compounds preferably dissolved in the fluid fior adjusting the pH to a level for coupling may include the organic amines 'such as described in Examples 3- 5, amongst' others including monoethanol amine,- triethanol amine and other organic amines, ammonium hydroxide, ammonia gas, or inorganic bases such as sodium hydroxide, potassium hydroxide, zinc hydroxide or other water soluble hydroxides or salts formed of strong bases and Weak acids.

While it is more economical to place the expensive diazo dye forming component in the carbon sheet or imaging composition whereby limited use is made thereof in the production of copy, it will be evident that the concepts of this invention may be achieved when the coupler is compounded as a component of the carbon coating or imaging composition and the diazo dye forming component is contained in the wetting out fluid in combination with the base substance, when necessary, for adjusting the pH, or else in the copy sheet wetted out with the solution of the base, when necessary, for adjusting the pH to the point where coupling can take place.

Example 8 A coating composition for the preparation of a transfer sheet may be formulated of the following:

Percent Carnauba wax 8.5 Oxidized micro Wax 14.0

Petrolatum 12.0 Mineral oil 15.5 Phloroglucinol 50.0

Application onto a suitable base sheet may be made in weights of about 20 pounds per 3000 square feet from a hot melt raised to a temperature of about 80-90 C.

When the coating composition is formulated to contain the coupler as described in Example 8, the fluid for wetting out the copy sheet for purposes of extracting a proportion of the phloroglucinol from the imaged master whereby the dyestuff is developed by reaction in the copy sheet may be formulated of the following:

Example 9 Percent Ammonium hydroxide 2.0 Methanol 98.0

In operation 'of the process, the copy sheet is adapted to have been treated to contain a diazo dye intermediate such as p-diazo benzyl aniline sulfonate for reaction with the coupler transferred from the imaged master. In the alternative, the fluid may be formulated to contain the diazo and base as in the following example:

Example 10 Percent p-Diazo diethyl aniline zinc chloride 1.0 Methanol 93.0

Diethanolamine 6.0

By way of further modification, the coupler and the alkali, when necessary, may be compounded in the carbon sheet and the diazo dye forming component placed in the fluid, as illustrated by the following examples:

Example 11 Carbon coating composition:

Percent Carnauba wax 5.0

Micro wax 20.0

Paraflin wax 15.0

Petrolatuin 15.0 Phloroglucinol 35.0

Trieth-anol amine v 10.0

The combination described may be processed in the usual manner for spirit duplication to form a dark purple water insoluble dye in the imaged areas of the copy sheet. When the diazo component is provided as an ingredient in the fluid or as a component of the copy sheet introduced, as by impregnation, it is imperative that the dye intermediate be relatively free of color and sufliciently stable to prevent the development of background color in'the copy sheet.

As previously pointed out, the coupler or the diazo dye forming compound may be contained in the carbon coating composition, as illustrated in Examples 1 and 6, and the coupler for use with compositions of the type set forth in Examples 1 and 6 or the diazo component for use with composition of Example 8 may be disposed in the base sheet, but, in any event, at least one of the components for developing the dye must be contained in the imaging material transferred by carbon or by typewriter or by writing ink to the master. When embodied in the base sheet, such dye forming components may be incorporated by conventional coating or impregnating systems or by incorporating the component as an ingredient in the fiber containing slurry from which the copy sheet is formed. Under these circumstances and under circumstances Where the component is applied as a part of the fluid over the entire surface of the copy sheet, it is desirable that the components in combination with the alkali be sufficiently stable to avoid the development of background color on the copy sheet.

By way of still further modification, it is possible to embody one of the water or alcohol soluble dye forming components substantially free of color in the imaging material and then produce copy in the impression material by first wetting out the copy sheet with the solvent or diluent to eflect transfer of some of the dye forming component from the imaged master to the copy sheet and subsequently wetting the copy sheet with a second fluid containing the coupler, in the event that the imaging material contains diazo, or else with a diazo intermediate in the event that the coupler is embodied as an ingredient in the imaging material or else with a base in the event that the diazo and coupler are applied one from the imaged master and the other with the first fluid for transfer of material from the master to the copy sheet or else with a base when the coupler and the diazo compound are present together in the imaged master.

, While description herein has been confined chiefly to the use of a water or alcohol soluble azo dye forming component in the transfer sheet for reaction in alkaline medium with other components to form an azo dyestuff in the copy sheet upon transfer, it will be apparent that when the coupler exists alone in the transfer coating of the carbon sheet and the diazo for reaction therewith exists in the fluid or in the copy sheet wetted with the fluid, the necessity for acidic medium for stabilization of the diazo against premature reaction with the coupler to form the azo dye is absent with the result that diazo compounds and couplers capable of reaction upon contact may be used and that such reaction may be adapted to occur in acidic as well as in alkaline medium thereby to eliminate the limitation with respect to pH control or the presence of alkali in the fluid for adjustment of pH to effect reaction.

It will be understood that in the practice of this invention, the couplers of Examples 3, 4 and 5 may be embodied instead of the diazo compounds in Examples 1 and 6 and that the diazo compounds of Examples 1 and 6' may be substituted for the couplers of Examples 3, 4 and 5 in amounts equivalent to the concentration of the components for which the substitution is made in the practice of the phase of the invention described and claimed herein where the coupler is in the transfer sheet and the diazo is present in the fluid or copy sheet. It will be further understood that when present in the copy sheet, the diazo may be incorporated as an incidence to the formation of the sheet but preferably by application of the diazo as a surface coating on the sheet by application from solution in advance of wetting the copy sheet with the spirit solvent prior to contact with the imaged master for transfer, of coupler from the imaged areas to produce copy by reaction to form the azo dyestuif.

It will be further understood that the concepts of this invention may be practiced by the use of imaging materials in the form of typewriter ribbons, Writing ink, drawing crayon or the like embodying one or more of the substantially colorless dye forming components of the type described for preparation of the imaged master and that other components for completing the reaction to form the dyestufl may be placed in the fluid or in the copy sheet for reaction to develop the dyestuff as an incidence to the transfer of the dye forming component from the imaged master to the copy sheet. The composition of such inking materials or crayons may be formulated with a conventional base containing the dye forming component in relatively high proportion.

It will be apparent from this description that a completely new and improved duplicating process is provided herein capable of use in conventional hectograph duplicating machines to produce copy of improved quality formed of a water insoluble dyestuif. Until the dye is formed in the copy sheets, the elements involved in the preparation of the master or in the manufacture of imaging compositions and the elements present in materials used to produce the imaged master or the imaged master itself remain wholly free of color transfer value and therefore avoids one of the most objectionable features of processes which have heretofore been employed. In addition, black copy or copy of various colors unlimited in their range may be produced and such copies of different colors may be produced from a single master depending upon the coupling agent employed or the dye components employed.

It will be evident also that the master sheet, being free of color, may be handled in the normal manner without dirtying ones hands or clothing and that it may be filed away for subsequent use to produce additional copies without loss of definition or quality of the copy produced.

It will be further understood that changes may be made in the details of composition, arrangement and method of use without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. A multiple duplicating process for ofiice work, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating substantially free of any dye color and containing at least one of the components for reaction to form an azo dyestuff, imaging the master by transfer of coating from the transfer sheet in response to applied force, Wetting the surfaces of the copy sheets with a solvent for the azo dye component in the imaged master, contacting the imaged surface of the master with the copy sheets wetted with a fluid containing a solvent for the dye-forming component to cause some of the material to be leached from the master for transfer to the copy sheets and form a latent image thereon, and then contacting the surface of the copy sheets having the latent image with a solution containing the other ingredient to introduce the other ingredient for reaction with the azo dye component to develop the azo dyestufl in the latent image to form the image in the copy sheets.

2. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a diazo compound free of color transfer value, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, wetting the surface of the copy sheets with a fluid containing a solvent for the diazo compound, contacting the imaged surface of the master with copy sheets wetted with the fluid containing a solvent for the diazo compound to cause some of the diazo to be leached from the imaged master for transfer to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets with a fiuid containing a coupler for reaction with the diazo to develop the image as an azo dyestulf in the copy sheets.

3. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a stabilized diazo compound soluble in a medium selected from the group consisting of alcohol and water, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, wetting the surface of the copy sheets with a fluid containing a solvent for the diazo compound, contacting the imaged surface of the master with copy sheets wetted with the fluid containing a solvent for the diazo compound to cause some of the diazo to be leached for trans fer from the imaged master to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets with a fluid containing a coupler and a base for adjustment of the pH to enable coupling reaction to take place to form the azo dyestuff and thereby develop the image in the copy sheets.

4. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a diazo compound stabilized to pre vent reaction with a coupler to form an azo dyestuff while in a strongly acidic medium, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, Wetting the surface of the copy sheets with a fluid containing a solvent for the diazo compound and also containing a coupler, contacting the imaged surface of the master with the copy sheets wetted with the fluid containing a solvent for the diazo compound and coupler to leach some of the diazo from the imaged master for transfer to the copy sheets to form a latent image thereon while maintaining the materials at a pH sufliciently acidic to prevent coupling, and subsequently wetting the surface of the copy sheets with a base for adjusting the pH to a level where reaction can take place between the diazo and coupler to form the azo dyestufi thereby to develop the image in the copy sheets.

5. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a diazo compound stabilized against reaction with the coupler while in a strongly acidic medium, imaging the master by transfer of coating from the transfer sheet to the master sheet in response to applied force, wetting the surface of copy sheets with a fluid containing a solvent for the diazo compound and containing a base, contacting the imaged surface of the master with the copy sheets wetted with a. fluid containing a solvent for the diazo compound and a base whereby some of the diazo is leached from the imaged master for transfer to the copy sheets, and subsequently wetting the copy sheets with a fluid containing a coupler for coupling reaction with the diazo compound to form an azo dyestuif as the image in the copy sheets.

6. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a coupler capable of reaction with a diazo compound to form an azo dyestuif, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, Wetting the surface of copy sheets with a fluid containing a solvent for the coupler, contacting the imaged master with the copy sheets wetted with a fluid containing a solvent for the coupler for leaching some of the coupler for transfer from the imaged master to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets with a fluid containing a diazo compound for reaction with the coupler to form the azo dyestuff in the development of the image in the copy sheets.

7. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a coupler capable of reaction with the diazo compound at a pH above 3.5 to form an azo dyestuff, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, wetting the surface of copy sheets with a fluid containing a solvent for the coupler and a base for adjusting the pH to a level above 3.5, contacting the image master with the copy sheets wetted with the fluid whereby some of the coupler is leached for transfer from the imaged master to the copy sheets to form a latent image thereon, and subse quently Wetting the surface of the copy sheets with a fluid containing a stabilized diazo compound capable of reaction with the coupler at the pH level formed by the base to form an azo dyestuif.

8. The method of producing multiple copies by a planog'raphic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a coupler capable of reaction with a diazo compound at a pH above 3.5 to form an azo dyestuif, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, wetting the surface of copy sheets with a fluid containing a solvent for the coupler and a diazo compound stabilized against reaction with the coupler at a pH below 3.5 while maintaining the system at a pH below 3.5, contacting the imaged surface of the master with the copy sheets wetted with the fluid whereby some of the coupler is leached for transfer from the imaged master to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets with a fluid containing a base for adjustment of the pH above the level of 3.5

whereby coupling reaction takes place to form the azo dyestuff in the copy sheets.

9. The method of producing multiple copies by a planographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a coupler and a diazo compound stabilized against reaction with the coupler in a strongly acidic medium, imaging the master by transfer of coating from the transfer sheet to the master in response to applied force, wetting the surface of copy sheets with an acidic fluid containing a solvent for the diazo compound and coupler, contacting the imaged surface of the master with the copy sheets Wetted with the fluid whereby some of the diazo and coupler is leached for transfer from the imaged master to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets with a base for adjusting the pH to a level where coupling reaction can take place between the diazo and coupler to form the azo dyestuff.

1G. The method of producing multiple copies by a plan ographic process, comprising the steps of positioning the surface of a duplicating master in contact with the coated side of a transfer sheet having a transfer coating containing a coupler and a diazo compound capable of reaction with the coupler to form an azo dyestuif and a medium to prevent reaction prior to adjustment of the pH, imaging the master by transfer of coating from the master sheet to the master in response to applied force, wetting the surface of copy sheets with a fluid containing a solvent for the coupler and diazo, contacting the imaged surface of the master with the copy sheets wetted with the fluid whereby some of the coupler and diazo is leached for transfer from the imaged master to the copy sheets to form a latent image thereon, and subsequently wetting the surface of the copy sheets to introduce a medium for adjustment of the pH to a level where coupling reaction can take place between the coupler and diazo to form the azo dyestutf as the image in the copy sheets.

References Cited in the file of this patent UNITED STATES PATENTS 38,086 Underwood Mar. 31, 1863 1,514,222 Murray Nov. 4, 1924 2,146,976 Neidich Feb. 14, 1935 2,217,349 Neidich Oct. 8, 1940 2,234,648 Lubs Mar. 11, 1941 2,364,359 Kienle et a1 Dec. 5, 1944 2,526,995 Clark Oct. 24, 1950 2,596,756 Yutzy et a1 May 13, 1952 2,597,306 Eaton et a1 May 20, 1952 2,634,677 Klimkowski et al Apr. 14, 1953 

